The present invention relates to an arrangement for coupling waveguide modes between two waveguides via a semiconductor element, with the semiconductor element being inserted into a coupling aperture in a partition between the two waveguides and being in ground contact with this partition. In such an arrangement the semiconductor element has two connecting arms, one of which extends as a coupling probe into one waveguide and the other of which extends as a coupling probe into the other waveguide.
Such an arrangement is disclosed in a publication by I. Angelov, A. Spasov, I. Stoev, L. Urshev, entitled "Investigation of Some Guiding Structures for Low-Noise FET Amplifiers", European Microwave Conference 1985, pages 535-540. This publication describes a high frequency amplifier whose amplifier element is a field effect transistor (FET). The FET is coupled in the manner described above to an input waveguide and to an output waveguide, both being disposed one behind the other along a common axis. This known arrangement has a drawback in that its structural length is unusually large, particularly if a multistage amplifier is involved.